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Remote sensing for resources development and environmental management
Damen, M. C. J.

lagery as a coun-
Is fully realised
n made no mention
al remote sensing
is imagery is now
r of planets and
sf other planets,
^ientific imagin-
rticipants while
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of the last few
te following main
:s that has freed
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srding altitudes
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ximately 18,000-
t include super-
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he possibilities
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usually years or
biting resource
olution of less
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t (interval of a
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on and temporal
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Lzation methods
telemetering of
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:s high in this
digital methods
jh geometric and
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and for (feature
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r our heads from
e the satellite
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: the recordings
ng the informa
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r elopment, there
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us GIS/LIS hold
¡ part of a lar-
tioned, several
¡ally were using
ogy and oceano-
graphy, have developed a great interest in satellite
remote sensing, particularly in low resolution ima
gery. The field of application of aerospace data for
resource development and related subjects thus has
grown substantially. This, however, is only one and
even relatively minor aspect of the matter. Resource
surveyors share their interest in aerospace techno
logy with photogrammetrists, making and updating
topographic maps, with geodesists and geophysicists
measuring the shape of the Earth and with astron
omers exploring our planetary system and even the
universe. The breakthrough of space technology has
the effect of rapidly pushing forward the frontiers
of science! In fact, although nowadays entire satel
lite systems are devoted to resource studies of our
planet, very substantial sums are spent on other,
quite different, aspects of space research (telecom
munications for example). Cynical people will say
that governments do not usually spend such vast
amounts of money for the sake of pure science and
that the military potentials of rockets and space
craft are the reasons behind it. These potentials
undeniably exist but need not worry us unduly as
resource surveyors. There is, in fact, nothing new
in this respect: aircraft development has in the
past hardly been influenced by considerations of
resource surveying, but through the years photogram
metrists and photo-interpreters alike have neverthe
less greatly benefitted from it. Also, I feel that
the military potentials are just a part —and prob
ably not even the most crucial part—of the engine
pushing space research. A space-industrial complex
is developing and technologic breakthroughs in
fields such as super computers and micro-chips are
triggered. We are moving quickly to the post-indus
trial space era with its inherent problems related
to advanced technology, economic growth, employment,
utilization of human resources, social discrepancies
between various parts of the globe, preservation of
our cultural heritage, etc. We resource surveyors
nowadays are like the small sucker fish that is
attached to the skin of a whale (or shark), while
being thrust forward by the whale of space technol
ogy, we —living in symbiosis with it— have to find
applications that are justifiable from an economic,
scientific and social point of view.
The rise of aerospace technology has affected re
source surveying in various ways by making images of
different types and scales available. Nevertheless,
the same basic methods of image interpretation still
apply throughout, —the essence of which is indi
cated in Fig. 1. An eye-brain interactive system
based on visible image density (greytone, colour)
and relief elements leads to an assessment of the
(usually) invisible resources, through a reiterative
process of observation deduction, induction and
verification that generates hypotheses, interpre
tations and conclusions. Obviously, technologically
perfected data acquisition and scientifically well-
trained interpreters are of equal importance for
obtaining optimum results, in much the same way as
refined equipment and a skilled watchmaker are re
quired to produce a good watch.
The density can be pictured in grey tones or in
colours and relates specifically to the vegetal
cover, to surface water, ice and snow and to barren
soil or rock. The relief can best be pictured
stereoscopically, although also monoscopically some
data can be obtained through shadow (density) pat
terns. It is particularly important as an indicator
of terrain forms. While in stereoscopic photo-inter
pretation both density and relief criteria played a
rather balanced part, the development of airborne
satellite remote sensing during the last decades has
strongly enphasised the analysis of density pat
Figure 1. The reiterative process of eye-brain
interaction in image interpretation.
terns. Image interpretation, especially in the
fields of the "green" and "blue" sciences (vegeta
tion, land use, surface hydrology, oceanography),
has benefitted from this. Although "brown" (earth)
sciences have also been positively affected by
improved density analysis, a stronger impetus for
them can be expected in the years to come: With the
advent of SPOT and also metric camera/large format
camera, etc., stereoscopic relief has been intro
duced as a criterion in the interpretation of or
bital imagery.
When briefly outlining the increased capacity of
image interpretation the following picture emerg
Multi-spectral recordings have considerably im
proved both qualitative and quantitative image
interpretation methods. The possibilities for re
cognition and identification of objects by visual,
qualitative means have increased distinctly but the
scope in the context of quantitative studies of
spectral signatures and digital data processing is
enormous. Quantitative relief analysis using satel
lite remote sensing is as yet much less advanced
and is a promising area of research now that
stereoscopic satellite imagery has come on the
Multi-temporal recordings have given new impetus
to the field of dynamic image interpretation. It
may relate to monitoring of daily/hourly changes in
cloud patterns, of seasonal changes in vegetation
patterns, of sea water temperatures and of sudden
or gradual changes in the land surface, such as
coastlines and river courses. The requirements for
spatial and temporal resolution vary with the type
of phenomenon concerned and the affected surface
area. Generally there is a trade-off between low-
resolution images/data obtained at short intervals
and high-resolution images taken at larger inter
vals. In this respect, there is ample scope for
both high and low-resolution satellite data. A
special case is the monitoring of sudden and often
catastrophic natural disasters, such as floods.
Time-specific recordings are then required and the
present problem is that low-resolution data are
inadequate and high-resolution imagery from orbit
ing satellites may not be available either because
there is no pass at the required time or because of
cloud cover. More frequent satellite passes and/or
all-weather (radar) systems are thus badly needed.
An often insufficiently understood characteristic
of disaster surveying using satellite imagery as a
tool is that the hazard zoning usually has to be
established in advance on the basis of the terrain
configuration visualized on earlier, pre-disaster,
images which are then to be matched with the time-
critical images taken during the disaster.
Multi-phase recording has been advocated
as a